Recording type optical discs have the characteristics that can record a large amount of information and enable media conversion. The recording of information into an optical disc that is a recording medium is performed by irradiating the information recording surface of the optical disc with laser beam of higher power than reconstructed light and thermally forming a recording mark. The reproduction of information is performed by condensing the laser beam on the information recording surface of the optical disc and detecting the reflected light modulated by the recording mark. The recording type optical disc are roughly divided into three types of magneto-optical, phase change, and ablation discs. There are a MO of a magneto-optical type and a DVD-RAM of a phase change type as rewriting applications, and an ablation type disc that uses organic coloring matter and is typified by a CD-R and a DVD-R has come into wide use as a write-once application in which data can be recorded only once.
Among various optical discs, attention is being paid to a DVD that can handle a large amount of information, such as a computer, images, and music, by a common medium as a new mass storage medium, such as a PC and AV equipment, and the market is expanding. The second generation 4.7 GB DVD-RAM has appeared as the mass storage media.
Since a smaller mark needs to be formed precisely to obtain a high-density recording type optical disc, the precise control of recording power (laser beam power for recording) is necessary. However, it is difficult to form a recording mark of a predetermined size on the information recording surface in a practical optical disc apparatus due to the recording sensitivity dispersion of the recording film of a recording medium even if the laser output is kept constant because of the effect caused by a dynamic change, such as an ambient temperature, a laser wavelength, or distortion of an optical spot. Accordingly, a technique called recording compensation learning that obtains the optimum value of the recording power and secures a recording margin by performing a trial write operation in the test area provided in the optical disc before the information is recorded has been used up to this date.
Regarding the recording compensation learning technique, an example is disclosed in JP-A No. Hei 11-296858. In optical discs for recording, there are two recording methods for computers and AV equipment. Regarding the former, to secure the reliability of recorded information, a reproduction check and verify are performed in the rotation after the information is recorded. If an error rate is high in this reproduction check, recording is retried and this is called retry processing. For a DVD-RAM, data is recorded at a random position on an optical disc according to a command from a host computer in a unit of 2,048 bytes. The data of the single unit is called one sector and collected 16-sector data may be called one block.
On the contrary, in the AV equipment that mainly uses moving image recording, since real time recording is used, recording without verify is presupposed. The real time recording is a recording method standardized in the DVD video recording standard of the DVD-RAM Book 2.0, and is a system for recording continuously-timed information, such as moving images and voices. This recording method continuously records data without performing verify and a retry not to omit the recorded information.
Since the DVD-RAM enables a multi-purpose application, in some case, personal computer data and the image information of the AV equipment are mixedly recorded on the same disc in the same apparatus. In such case, the recording into a conventional rewrite-enable optical disc is performed using the same recording power instead of the recording methods (real time recording and recording with verify).
The recording according to the recording compensation learning system is performed to reduce the effects of the dispersion of an information recording medium and an information recording apparatus and a dynamic change by ambient environment, such as temperatures. In actual, there are many factors that narrow the margin (range of the recording power that can normally perform recording) of the laser power for recording due to the following factors, and the power margin for recording needs to widely be secured to ensure the high reliability of the recorded information.
Hereupon, the concept of the recording power setting considered regarding the power margin of an optical disc for recording is described below.
FIG. 2 shows the relationship of a jitter when the recording power and the recorded part are reproduced. At the low power side, the formation of a recording mark becomes unstable and the jitter suddenly increases. In particular, spot distortion is cited as a dominant change factor that deteriorates the recording power margin. The occurrence factors of the spot distortion include coma due to a disc tilt, spherical aberration due to the dispersion of disc plate thickness, and focal misalignment due to servo tracking misalignment.
FIG. 3 shows the relationship between the jitter increase and recording power at the high power side. The dominant mechanism of the jitter increase in the recording of the high power side is the effect due to the cross erase from the adjacent track, and the higher recording power track frequently receives the effect from the adjacent track. The cross erase indicates that part of the recording mark of the track due to the thermal effect when data is recorded in the adjacent track is erased (because a write-once-read-only DVD-RAM or the like uses a phase change, it is re-crystallized) and signal quality deteriorates. In an optical disc apparatus, care needs to be taken not to deteriorate the signal quality until the adjacent track cannot be reproduced by the cross erase.
When the practical optimum recording condition is obtained, the recording power in which a recording mark can stably be formed, and, still more, that will not affect the adjacent track needs to be set in consideration of the factors that determine the jitters of both sides (high power and low power) of the power margin. For the power setting, the learning is performed at the predetermined place of the optical disc and the recording power is determined.
When the information recording method is a recording with verify, since it is the recording method used to record management data, overwrite that rewrites the same part many a time, such as update of the management data, frequently occurs. The management data extends over multiple tracks on the disc. Accordingly, when attention is paid to one block, the overwrite of tracks on both sides frequently occurs. This indicates that the tracks are affected (meshed part) by the cross erase from both the sides as shown in FIG. 12(a). The deterioration of a recording mark due to the cross erase decreases a regenerative signal amplification level and makes a signal to noise (S/N) ratio worse. Further, Every time the overwrite that updates management information is performed, since recording conditions change due to disturbance, such as temperature, spot distortion, and track offset, the cross erase further becomes easy to occur to the adjacent track in accordance with the frequency of the overwrite. For the state of things, an example in which the track offset occurs due to a disc tilt or the like is typically shown in FIG. 13(a). For the recording with verify, since the recording conditions change every time the overwrite is performed, the offset direction and quantity change. Accordingly, the cross erase may frequently occur against the track adjacent to the direction. In general, the cross erase due to disturbance or the like is prevented from occurring by suppressing the recording power in consideration of these effects. For the recording with verify, since recording is retried changing a parameter or the like regarding the part where a recording mark could not be formed correctly by suppressing the recording power, the reliability of the recorded information can be secured. However, for the real time recording, since verify and a parameter change or retry operation are not performed, how the reliability of the recorded information is secured comes into question.
An object of the present invention is to solve the above problems and secure the reliability of the recorded information for the real time recording.
The present invention relates to a record-enable optical disc apparatus, and, more particularly, to a recording method.
The problems noted above can be solved by the following means.
According to an aspect of the present invention, the optical disc apparatus has a system controller that receives a recording control command via an interface, a recording control block that receives a recording method command signal and recording data from the system controller, sets a recording power level in accordance with the recording method specified with the recording method command signal, and converts recorded information to the format of a recording mark and generates a recording pulse, and an optical head that modulates the power of laser beam using the recording pulse sent from the control block and records the recording data on an information recording medium, and is characterized in that information is recorded in the information recording medium according to at least two information recording methods using different recording power respectively.
Further, according to another aspect of the present invention, the two information recording methods have recording with verify and real time recording, and the recording power that records information uses the recording power determined by recording compensation learning and the higher power than the recording power obtained by the recording compensation learning. The recording power used in the two information recording methods may also use the recording power determined by different recording compensation leaning respectively.
Furthermore, according to another aspect of the present invention, it is also effective to record one track or more at the head and end of the file of the data recorded for the real time recording using lower recording power, it is also effective to record the recording data of the number of blocks including the one track or more at the head and end of the file of the data recorded for the real time recording using the lower recording power, and it is also effective to record only the recording data of the number of sectors for one track or more at the head and end of the data recorded for the real time recording using the lower recording power.
Moreover, according to another aspect of the present invention, it is also effective to determine the recording power toward the radial direction based on the linear approximation of the recording power obtained by the recording compensation learning respectively in which the recording power is obtained on the inside tracks and outside tracks respectively according to the two information recording methods, in the mode in which the recording data is recorded at a fixed angular velocity.
According to another aspect of the present invention, the information recording apparatus that uses the optical disc apparatus has an input unit that inputs either moving image information or voice information or both, a unit that digitally compresses input data, an optical disc that can reproduce recorded data, and a controller, and uses any form of the optical disc apparatus.
According to another aspect of the present invention, In particular, the information recording apparatus as a video camera has an image pick-up lens, an image sensor that converts an image focused by the image pick-up lens, a unit that digitally compresses the output of the image sensor, an optical disc apparatus that can reproduce recorded data, and a controller, and uses any form of the optical disc apparatus.
Further, the digital compression unit uses the MPEG-2 system.
Furthermore, as more specific recording data, the information recorded for the recording with verify is navigation data, and the information recorded for the real time recording is presentation data.
According to the unit, when the real time recording is performed to an information recording medium, the edge of a recording mark is stabilized by recording the recording mark using the higher recording power obtained by the recording compensation learning and the jitter is improved. A more detailed description is as follows.
When the recording power is shifted to the high power side according to the value obtained by the learning as described above, the cross erase due to thermal interference with the adjacent track is feared. However, it becomes known that there is a margin against this effect for the real time recording. The reason is described below. As shown in FIG. 4, for a DVD-RAM, an optical disc 1 sequentially arranges a pair of an address part 13 that indicates its physical position every unit information and a track 12 that records recorded information, and the track 12 has the structure in which the track of a land 10 that is the optical disc substrate surface every track and the track of a groove 11 that is the slot provided on the substrate surface are alternately replaced every round. For the real time recording, the track that is alternately adjacent to the land 10 and the group 11 from the inside tracks is sequentially recorded only once toward the outside tracks. This indicates that there are two characteristics advantageous for the cross erase. First, for the real time recording, since data is successively recorded from the inside tracks toward the outside tracks and there is no retry, the effect due to the cross erase may be considered only once when the outside track of the track is recorded. This indicates that for the recording of the management information, as shown in FIG. 12(a), both sides of the recording mark of the track are erased due to the cross erase, whereas for the real time recording, such as moving image data, as shown in FIG. 12(b), the effect of the cross erase is produced only from the outside. Therefore, the decrease of a regenerative signal level is slight. Secondly, as shown in FIG. 13(b), for the real time recording, since data is recorded only once in the same condition, the recording mark of each track is offset in the same direction even if track offset occurs. Since the distance from the mark of the adjacent track does not change substantially, most of the effects due to the track offset can be ignored. Accordingly, for the real time recording, the ratio at which the effect of the cross erase is received is considered exceedingly low compared with the recording with verify. The result of an experiment shown in FIG. 5 proves that the jitter of real time recording 15 is lower than the recording with verify 14 in the area where the recording power is high, and the consideration described above is backed up.
The object described above can be attained by applying the result and setting recording power 17 for the real time recording higher than recording power 16 for the recording with verify.
Besides, this system can also be applied to not only a phase change optical disc and but also a magneto-optical disc and an ablation type write-once optical disc.
According to the present invention, an optical disc apparatus provided with an optical head that records recording data on an information recording medium, the reliability of recorded information can be secured by recording information in the information recording medium using different recording power respectively according to at least two information recording methods.
Further, in particular, when the two information recording methods are the recording with verify and the real time recording, the reliability of the recorded information for the real time recording can be secured.